U.S. patent application number 10/678111 was filed with the patent office on 2004-04-22 for polymerizable liquid crystals.
This patent application is currently assigned to BASF Aktiengesellschaft. Invention is credited to Haremza, Sylke, Parker, Robert, Prechtl, Frank, Schmidt, Hans-Werner, Schmitt, Gerold, Schneider, Norbert, Schuhmacher, Peter.
Application Number | 20040075080 10/678111 |
Document ID | / |
Family ID | 7637430 |
Filed Date | 2004-04-22 |
United States Patent
Application |
20040075080 |
Kind Code |
A1 |
Prechtl, Frank ; et
al. |
April 22, 2004 |
Polymerizable liquid crystals
Abstract
Disclosed are polymerizable liquid-crystalline compounds of the
general formula (I) 1 where A.sup.1 and A.sup.2 are identical or
different and are each a crosslinkable group; the radicals X are
identical or different and are each a single bond, --O--, --S--,
--C.dbd.N--, --O--CO--, --CO--O--, --O--CO--O--, --CO--NR--,
--NR--CO--, --NR--, --O--CO--NR, --NR--CO--O--, --CH.sub.2--O-- or
--NR--CO--NR, in which R is H or C.sub.1-C.sub.4-alkyl; and M is a
mesogenic group, a process for their preparation and their use for
preparing cholesteric phases.
Inventors: |
Prechtl, Frank; (Frankfurt,
DE) ; Parker, Robert; (Mannheim, DE) ;
Schuhmacher, Peter; (Mannheim, DE) ; Schneider,
Norbert; (Altrip, DE) ; Haremza, Sylke;
(Neckargemund, DE) ; Schmidt, Hans-Werner;
(Bayreuth, DE) ; Schmitt, Gerold; (Bayreuth,
DE) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
BASF Aktiengesellschaft
Ludwigshafen
DE
|
Family ID: |
7637430 |
Appl. No.: |
10/678111 |
Filed: |
October 6, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10678111 |
Oct 6, 2003 |
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09824022 |
Apr 3, 2001 |
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6699405 |
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Current U.S.
Class: |
252/299.62 ;
252/299.01; 252/299.66 |
Current CPC
Class: |
C09K 19/2007 20130101;
C09K 2323/00 20200801; C09K 2019/0448 20130101; C09K 19/38
20130101; C09K 19/00 20130101; Y10T 428/10 20150115 |
Class at
Publication: |
252/299.62 ;
252/299.66; 252/299.01 |
International
Class: |
C09K 019/52; C09K
019/32; C09K 019/12 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 3, 2000 |
DE |
10016524.9 |
Claims
We claim:
1. A polymerizable liquid-crystalline compound of the general
formula (I) 42where A.sup.1 and A.sup.2 are identical or different
and are each a crosslinkable group; the radicals X are identical or
different and are each a single bond, --O--, --S--, --C.dbd.N--,
--O--CO--, --CO--O--, --O--CO--O--, --CO--NR--, --NR--CO--, --NR--,
--O--CO--NR, --NR--CO--O--, --CH.sub.2--O-- or --NR--CO--NR, in
which R is H or C.sub.1-C.sub.4-alkyl; and M is a mesogenic
group.
2. A compound as claimed in claim 1, wherein A.sup.2 is ortho to
A.sup.1 at each occurrence.
3. A compound as claimed in one of the preceding claims, wherein
A.sup.1 and A.sup.2 are each, independently of one another, a group
of the formula Z-X-(Sp).sub.n- where Z is a crosslinkable radical;
X is as defined above; Sp is a spacer having from 1 to 30 carbon
atoms, in which the carbon chain may be interrupted by ether
oxygen, thioether sulfur or nonadjacent imino or
C.sub.1-C.sub.4-alkylimino groups; and n is 0 or 1.
4. A compound as claimed in claim 3, wherein Z is selected from:
43where the radicals R are each, independently of one another,
C.sub.1-C.sub.4-alkyl.
5. A compound as claimed in claim 3 or 4, wherein Sp is selected
from: --(CH.sub.2).sub.p--,
--(CH.sub.2CH.sub.2O).sub.mCH.sub.2CH.sub.2--,
--CH.sub.2CH.sub.2SCH.sub.2CH.sub.2--,
--CH.sub.2CH.sub.2NHCH.sub.2CH.sub- .2--, 44where m is from 1 to 3
and p is from 1 to 12.
6. A compound as claimed in one of the preceding claims, wherein M
is selected from groups of the general formula II: 45where X is as
defined above, and Q is substituted or unsubstituted alkylene or a
substituted or unsubstituted aromatic bridging group.
7. A compound as claimed in claim 6, wherein the aromatic bridging
group is selected from 46and substituted analogs thereof.
8. A process for preparing a compound as claimed in claim 1, which
comprises reacting a compound of the formula III 47where A.sup.1
and A.sup.2 are as defined above and X' is a reactive side group,
with a mesogen compound of the general formula IV X"--M--X" (IV)
where M is as defined above and X" is a reactive side group, X' and
X" being selected such that they are capable of forming group
X.
9. A process as claimed in claim 8, wherein a mesogen of the
formula IV where X" is OH is reacted with a compound of the formula
III where X' is --COOH or --COHal, where Hal .dbd.F, Cl, Br or
I.
10. A composition comprising at least one compound as claimed in
one of claims 1 to 7 and, if desired, further components selected
from cholesteric, crosslinkable or noncrosslinkable groups,
inorganic pigments, colorants and polymerizable or nonpolymerizable
diluents or carriers.
11. A pigment comprising at least one compound as claimed in one of
claims 1 to 7 in crosslinked form.
12. A coating composition comprising a composition as claimed in
claim 10 or a pigment as claimed in claim 11.
13. The use of a compound as claimed in claims 1 to 7 for producing
optical elements, such as, in particular, filters and polarizers,
coating compositions, effect films, cosmetic compositions and
single- or multilayer cholesteric special-effect pigments.
Description
[0001] The present invention relates to novel polymerizable
liquid-crystalline compounds, to a process for their preparation,
to compositions comprising these compounds, and to coating
compositions and pigments based on these compounds for various
applications.
[0002] Aligned, low molecular weight liquid crystals can be
permanently fixed by UV polymerization, since UV polymerization is
so fast that relaxation of the aligned liquid crystals is not
possible. When crosslinkable cholesteric liquid crystals or
crosslinkable mixtures of nematic liquid crystals and chiral
dopants are used, UV polymerization leads to cholesteric networks
exhibiting the characteristic optical properties of a cholesteric
mesophase. It is of particular importance that the formation of
such networks stabilizes the color flop effect, i.e. the property
of a cholesteric liquid crystal to appear in a different color
depending on the viewing angle. This significantly simplifies the
preparation of cholesteric special-effect or color flop
pigments.
[0003] Cholesteric pigments are platelet-shaped particles
exhibiting shape anisotropy which are prepared from the
photocrosslinkable, cholesteric starting mixture via a plurality of
process steps. Said starting mixture has to be converted, in its
mesophase, into an aligned film and fixed by subsequent UV
polymerization. At the same time, this step determines the
thickness of the platelet-shaped particles. The resulting
cholesteric network then has to be ground to pigment particles in
another process step.
[0004] Cholesteric color flop pigments of various compositions are
already known. Siloxane-based color flop pigments are described,
for example, in EP-A-0 601 483. Said pigments were prepared by
crosslinking cyclic siloxanes having both chiral and mesogenic side
groups via acrylate or methacrylate groups on the mesogenic side
groups and processing to pigments.
[0005] WO-A-97/27252 describes color flop pigments obtainable by
polymerizing mixtures comprising a chiral liquid-crystalline
polymerizable monomer, an achiral liquid-crystalline polymerizable
monomer and a chiral compound, and a polymeric binder and/or a
monomeric, polymerizable compound and/or a dispersion auxiliary.
WO-A-99/11733 describes an improved process for preparing color
flop pigments and numerous different types of crosslinkable
cholesteric mixtures. Suitable achiral liquid-crystalline
polymerizable monomers have the general formula
Z-Y-A-Y-M-Y-A-Y-Z
[0006] where M is a mesogenic group, A is a spacer group, Y is one
of various bridging groups and Z is a polymerizable end group.
Preferred radicals Z are acrylate radicals. Each monomer preferably
has two polymerizable groups Z.
[0007] EP-A-0 675 186 describes photocrosslinkable liquid crystals
comprising four crosslinkable groups per molecule. The compounds
have the following general formula 2
[0008] where the mesogen is a linear trinuclear group, B is a
bridge linking the two mesogens and each R is a crosslinkable
radical. The mesogen preferably comprises three bridged p-phenylene
groups, and the crosslinkable radicals R are in each case terminal
in p position. Said compounds are used for preparing optical
components. Their suitability for preparing crosslinked cholesteric
special-effect pigments was not investigated. Said compounds have
the disadvantage that the crosslinking density per mesogen unit
which can be achieved is low.
[0009] It is an object of the present invention to provide improved
crosslinkable achiral liquid-crystalline monomers, in particular
those which make it possible to prepare liquid-crystalline polymers
having relatively high crosslinking density.
[0010] We have found that, surprisingly, this object is achieved by
providing liquid-crystalline compounds of the formula (I) 3
[0011] where
[0012] A.sup.1 and A.sup.2 are identical or different and are each
a crosslinkable group;
[0013] the radicals X are identical or different, preferably
identical, and are each a single bond, --O--, --S--, --C.dbd.N--,
--O--CO--, --CO--O--, --O--CO--O--, --CO--NR--, --NR--CO--, --NR--,
--O--CO--NR, --NR--CO--O--, --CH.sub.2--O-- or --NR--CO--NR, in
which R is H or C.sub.1-C.sub.4-alkyl; and
[0014] M is a mesogenic group.
[0015] The compounds of the formula I according to the invention
are notable for the fact that they are capable of forming a
liquid-crystalline phase and stabilize this phase particularly well
and permanently owing to their increased crosslinkable group
content.
[0016] The present invention preferably provides compounds of the
general formula I, where A.sup.2 is ortho to A.sup.1 at each
occurrence.
[0017] Preference is likewise given to compounds of the general
formula I where A.sup.1 and A.sup.2 are each, independently of one
another, a group of the formula
Z-X-(Sp).sub.n-
[0018] where
[0019] Z is a crosslinkable radical;
[0020] X is as defined above;
[0021] Sp is a spacer having from 1 to 30 carbon atoms, in which
the carbon chain may be interrupted by ether oxygen, thioether
sulfur or nonadjacent imino or C.sub.1-C.sub.4-alkylimino groups;
and n is 0 or 1.
[0022] A.sup.1 and A.sup.2 are preferably identical.
[0023] According to a preferred embodiment Z is selected from:
4
[0024] where the radicals R are each, independently of one another,
C.sub.1-C.sub.4-alkyl, for example methyl, ethyl, n- or i-propyl or
n-, i- or t-butyl.
[0025] According to another preferred embodiment Sp is selected
from:
--(CH.sub.2).sub.p--,
--(CH.sub.2CH.sub.2O).sub.mCH.sub.2CH.sub.2--,
--CH.sub.2CH.sub.2SCH.sub.2CH.sub.2--,
--CH.sub.2CH.sub.2NHCH.sub.2CH.sub- .2--, 5
[0026] m is from 1 to 3 and p is from 1 to 12.
[0027] According to another preferred embodiment M is selected from
groups of the general formula II: 6
[0028] where
[0029] X is as defined above, and
[0030] Q is substituted or unsubstituted alkylene, such as linear
or branched C.sub.1-C.sub.12-alkylene, or a substituted or
unsubstituted aromatic bridging group.
[0031] Preferred aromatic bridging groups are selected from 7
[0032] and substituted analogs thereof. Substituted analogs of said
bridging groups can carry from 1 to 4 identical or different
substituents per aromatic ring, preferably one or two substituents
per ring or per bridging group. Suitable substituents are selected
from C.sub.1-C.sub.4-alkyl as defined above, nitro, halogen, such
as F, Cl, Br, I, phenyl or C.sub.1-C.sub.4-alkoxy, the alkyl
radical being defined as above.
[0033] The present invention likewise provides a process for
preparing compounds of the general formula I, which comprises
reacting a compound of the formula III 8
[0034] where A.sup.1 and A.sup.2 are as defined above and X' is a
reactive side group, with a mesogen compound of the general formula
IV
X"-M-X" (IV)
[0035] where M is as defined above and X" is a reactive side group,
X' and X" being selected such that they are capable of forming
group X.
[0036] The present invention provides in particular a process in
which a mesogen of the formula IV where X" is OH is reacted with a
compound of the formula III where X' is --COOH or --COHal, where
Hal.dbd.F, Cl, Br or I.
[0037] The present invention furthermore provides a composition
comprising at least one compound of the formula I and, if desired,
further components selected from cholesteric, crosslinkable or
noncrosslinkable groups, inorganic pigments, colorants,
photoinitiators, flow control agents, UV stabilizers, binders and
polymerizable or nonpolymerizable diluents or carriers.
[0038] Preferred cholesteric compounds are, for example, chiral
compounds of the general formulae Xa, b, c and d
(Z--X.sup.5).sub.nCh, (Xa)
(Z--X.sup.2--Sp--X.sup.5).sub.nCh, (Xb)
(Phu 1--X.sup.5).sub.nCh (Xc)
(Z--X.sup.2--Sp--X.sup.3--M--X.sup.4).sub.nX, (Xd)
[0039] where
[0040] Z is as defined above,
[0041] Sp is a spacer as defined above,
[0042] X.sup.2, X.sup.3 and X.sup.4 are each, independently of one
another, a chemical single bond, --O--, --S--, --O--CO--,
--CO--O--, --O--CO--O--, --CO--NR--, --NR--CO--, --O--CO--NR--,
--NR--CO--O-- or --NR--CO--NR, where at least one of the groups
X.sup.3 and X.sup.4 is --O--CO--O--, --O--CO--NR--, --NR--CO--O--
or --NR--CO--NR-- and R is C.sub.1-C.sub.4-alkyl;
[0043] X.sup.5 is as defined for X.sup.2, X.sup.3 and X.sup.4 or is
--CH.sub.2--O--, --O--CH.sub.2--, --CH.dbd.N--, --N.dbd.CH-- or
--N.ident.N--,
[0044] M is a mesogenic group as defined above,
[0045] P.sup.1 is a radical selected from hydrogen,
C.sub.1-C.sub.30-alkyl, C.sub.1-C.sub.30-acyl,
C.sub.3-C.sub.8-cycloalkyl- , unsubstituted or substituted by one
to three C.sub.1-C.sub.6-alkyl, and where the carbon chain of the
alkyl, acyl and cycloalkyl radicals may be interrupted by ether
oxygen, thioether sulfur or nonadjacent imino or
C.sub.1-C.sub.4-alkylimino groups,
[0046] n is a number from 1 to 6 and
[0047] Ch is an n-valent chiral radical.
[0048] Examples of radicals Ch are 91011
[0049] where
[0050] L is C.sub.1- to C.sub.4-alkyl, C.sub.1-C.sub.4-alkoxy,
halogen, COOR, OCOR, CONHR or NHCOR and R is
C.sub.1-C.sub.4-alkyl.
[0051] (The terminal dashes in the above formulae indicate the free
valencies).
[0052] Particular preference is given, for example, to the
following: 12
[0053] These and other preferred chiral components are mentioned,
for example, in DE-A 43 42 280 and in the prior German patent
applications 19520660.6 and 19520704.1.
[0054] Another preferred group encompasses chiral compounds of the
formula Xb or Xd in which
[0055] n equals 2,
[0056] Z.sup.1 is H.sub.2C.dbd.CH-- and
[0057] Ch is a chiral radical of the formula 13
[0058] and
[0059] Sp, X.sup.2, X.sup.3, X.sup.4, X.sup.5 and M are as defined
above.
[0060] Particularly preferred chiral components are the following
compounds (A) to (G): 1415
[0061] When the nonchiral compounds of the formula I are used in
combination with the above chiral compounds, the molar ratio of
nonchiral compound of the formula I to chiral compound of the
formula Xa, b, c or d is in the range from about 1:0.01 to 1:0.3,
in particular from 1:0.01 to 1:0.25.
[0062] Polymerization of the compounds or liquid-crystal
compositions according to the invention allows the
liquid-crystalline ordered state to be fixed. The polymerization
can be carried out, for example, thermally or photochemically,
depending on the polymerizable group. Other monomers can also be
copolymerized together with the compounds or liquid-crystal
compositions according to the invention. These monomers can be
other polymerizable liquid-crystalline compounds, chiral compounds,
which are likewise preferably copolymerized covalently, or
conventional crosslinking agents, such as polyvalent acrylates,
vinyl compounds or epoxides. Especially in the case of isocyanates,
isothiocyanates or epoxides as polymerizable liquid-crystal
compounds, the crosslinking agent is preferably a polyvalent
alcohol, meaning that, for example, urethanes can be formed. The
crosslinking agent must be matched in its amount to the
polymerization conditions in such a way that firstly satisfactory
mechanical stability is achieved, but secondly the
liquid-crystalline phase behavior is not impaired. The amount of
crosslinking agent therefore depends on the specific application of
the polymers. For the preparation of pigments, a relatively large
amount of crosslinking agent is advantageous, while for the
production of thermoplastic layers or, for example, for display
alignment layers, a relatively small amount of crosslinking agent
is necessary. The amount of crosslinking agent can be determined by
a few preliminary experiments.
[0063] A further modification of the polymerization products
prepared from the compounds or liquid-crystal compositions
according to the invention is possible by addition of polymeric
auxiliaries prior to polymerization. Auxiliaries of this type
should preferably be soluble either in the starting mixtures or
alternatively in an organic solvent which is compatible with the
starting mixtures. Typical representatives of polymeric auxiliaries
of this type are, for example, polyesters, cellulose esters,
polyurethanes and polyether- or polyester-modified or unmodified
silicones. The amount of polymeric auxiliary to be added, where
appropriate, for the desired purpose, its chemical nature and
possibly also the amount and nature of the solvent are generally
known to the person skilled in the art or can likewise be
determined experimentally by a few preliminary experiments.
[0064] Besides the compounds of the formulae I and Xa to d, further
compounds which are incorporated noncovalently into the polymeric
network can also be incorporated. These can be, for example,
commercially available nematic liquid crystals.
[0065] Further additives can be pigments, dyes, fillers,
stabilizers, such as, in particular, UV stabilizers, flow control
agents, photoinitiators, dispersants and the like.
[0066] The pigments can be inorganic compounds, for example iron
oxides, titanium oxide and carbon black, and the organic compounds
can be, for example, pigments or dyes from the classes of the
monoazo pigments, monoazo dyes and metal salts thereof, disazo
pigments, condensed disazo pigments, isoindoline derivatives,
derivatives of naphthalene and perylene tetracarboxylic acid,
anthraquinone pigments, thioindigo derivatives, azomethine
derivatives, quinacridones, dioxazins, pyrazoloquinazolones,
phthalocyanine pigments or basic dyes, such as triarylmethane dyes
and salts thereof.
[0067] The present invention furthermore provides pigments
comprising at least one compound of the formula I in crosslinked
form. The compounds of the formula I according to the invention can
be processed to cholesteric special-effect pigments in a
conventional manner in combination with conventional chiral
compounds, in particular compounds of the above formula Xa to d. A
crosslinkable mixture of these compounds is applied to a support in
a conventional manner, for example by spraying, rolling,
knife-coating, roller-coating, printing or casting, the cholesteric
phase is formed, i.e. aligned, crosslinked and, if desired, dried.
The cholesteric special-effect layer thus formed can then be
removed from the support in a conventional manner, and the
resulting flakes can be further comminuted and classified, if
desired. Pourable mixtures are preferably processed in casting
devices and under conditions as described, for example, in
WO-A-99/11733, which is incorporated herein by reference.
[0068] The layer thickness of the platelet-shaped pigments is from
0.5 to 20 .mu.m, in particular from 0.5 to 10 .mu.m, for example
from 0.5 to 3 .mu.m.
[0069] The diameter of the pigments according to the invention is
from about 1 to 500 .mu.m, in particular from about 3 to 100 .mu.m
or from 3 to 30 .mu.m and is about 2 to 20 times the pigment
thickness.
[0070] The pigments can also be in the form of multilayer pigments
comprising one or more cholesteric layers, one or more absorber
layers or one or more pigmented absorber layers. These are
obtainable, for example, in accordance with the processes described
in WO-A-99/11719, WO-A-99/11733 or PCT/EP 99/03106, which are
incorporated herein by reference.
[0071] The invention furthermore provides a coating composition
comprising a composition or a pigment as defined above. Preferred
coating compositions are in particular paints and varnishes, which
comprise not only the pigments or compositions according to the
invention but also customary paint and varnish additives, in
particular polymeric binders, dispersants and diluents. Suitable
additives are known to those skilled in the art and described, for
example, in WO-A-99/11733, which is incorporated herein by
reference.
[0072] The invention provides the use of a compound according to
the invention for producing optical elements, such as, in
particular, filters and polarizers, coating compositions, effect
films, cosmetic compositions and single- or multilayer cholesteric
special-effect pigments.
[0073] For the purposes of the present invention, the term "optical
elements" is taken to mean all articles which utilize the optical
properties of nematic and/or cholesteric liquid crystals. Specific
examples of these include retardation films, notch filters, color
filters for displays, polarizers, but also simply mirrors for
decorative purposes. The three-dimensional shape of the optical
elements can be planar, but also with a concave or convex curve. In
a particular embodiment, the polymerized films can be comminuted to
pigments, incorporated in conventional binders and applied to a
support by conventional application methods, such as spraying,
roller coating, casting, atomizing, knife coating or printing. The
optical elements preferably have a planar shape.
[0074] The application of the compounds of the general formula I or
mixtures comprising compounds of the general formula I is essential
for the quality of the optical elements, since the optical quality
of the layers is determined by the application method. Suitable
application methods are in general spraying, rolling, roller
coating, casting, knife coating and printing.
[0075] In a preferred embodiment the liquid-crystalline material is
dissolved in a readily volatile solvent in combination with any
additives necessary. Suitable solvents are THF, MEK, toluene, ethyl
acetate and butyl acetate. Additives which can be employed are
polymerization inhibitors or polymerization initiators, flow
control agents, aerating agents, adhesives etc. The isotropic
solution is transferred to a substrate via a conventional
applicator. After passing through a drying tunnel, in which the
solvent is removed, the wet film can be fixed with the aid of UV
radiation. The resulting films exhibit very high reflectivity.
These films are highly suitable as polarizers in LC displays. In
one embodiment, a number of layers of such films are laminated one
on top of the other by lamination processes, and a polarizer which
covers light throughout the visible spectrum can be obtained by
suitable choice of selective wavelengths of the selected films (EP
0 720 041).
[0076] Color filters can also be produced using mixtures comprising
compounds of the general formula I. To this end, the wavelengths
required can be applied specifically by application methods
customary to those skilled in the art. An alternative application
form utilizes the thermochromicity of cholesteric liquid crystals.
By adjusting the temperature, the color of the cholesteric layer
can be shifted from red via gray to blue. With the aid of masks,
certain zones can be polymerized specifically at a defined
temperature. The crucial parameter effecting the thermochromicity
and the handedness of the cholesteric mixture comprising compounds
of the cholesteric mixture comprising compounds of the formula I is
the choice of the chiral auxiliary. The chiral auxiliary determines
the handedness of reflected light and the thermochromicity of the
cholesteric system.
[0077] Besides the optical properties of cholesteric phases
comprising compounds of the general formula I, the nematic phase of
these substances is also suitable for use in optical elements. In
this case, the birefringence of such a system is utilized. Mention
may be made here, in particular, of retardation films.
[0078] The invention is illustrated below by means of a detailed
description of the synthesis of preferred mesogendiols and the
subsequent synthesis of preferred liquid-crystalline polymerizable
monomers of the formula I according to the invention.
[0079] A. Synthesis of Mesogendiols
[0080] 1. Synthesis of Binuclear Mesogendiols
[0081] 2,2'-Dimethyl-4,4'-dihydroxybiphenyl (1a) is synthesized
using known methods (Percec et al., Macromolecules (1996) 29, 3727;
Colon, J. et al., J. Org. Chem (1986) 51, 2627) in accordance with
the following reaction scheme 1: 16
[0082] 4-Chloro-3-methylphenol is acetylated and the acetylated
product is converted into 2,2'-dimethyl-4,4'-diacetyloxybiphenyl by
a Ni(0) coupling reaction. The acetyl group is removed by basic
hydrolysis and 2,2'-dimethyl-4,4'-dihydroxybiphenyl is released
from the phenolate by addition of hydrochloric acid. The product is
purified by vacuum distillation and subsequent recrystallization
from toluene. After purification, the mesogendiol is obtained in
61% yield.
[0083] 2. Synthesis of Trinuclear Mesogendiols
[0084] The trinuclear mesogendiols consist of a central
hydroquinone unit and two terminal 4-hydroxybenzoic acid units.
They have the following structure: 17
[0085] Both the hydroquinone unit and the two 4-hydroxybenzoic acid
units can carry one or more substituents R.sup.1--R.sup.4 or
X.sup.1--X.sup.4.
[0086] Trinuclear mesogendiols can be synthesized in principle via
two routes. The choice of synthesis route depends in particular on
the substitution pattern of the central hydroquinone unit. This
pattern determines the synthesis route for preparing the trinuclear
mesogendiols.
[0087] Mesogendiols containing unsubstituted or only
methyl-substituted hydroquinone units can be prepared, as described
in DE-A-197 16 822, in accordance with the following reaction
scheme 2, exemplified for the synthesis of
1,4-phenylene-bis-(4-hydroxy)benzoate (2a): 18
[0088] 4-Hydroxybenzoic acid and hydroquinone in a molar ratio of
2:1 are added to p-xylene. Neither 4-hydroxybenzoic acid nor
hydroquinone is completely soluble in p-xylene. Azeotropic
esterification using p-toluenesulfonic acid (p-TSS) as a catalyst
yields the trinuclear mesogendiol
1,4-phenylene-bis-(4-hydroxy)benzoate which is again insoluble in
xylene. The mesogendiols prepared by this method are obtained in
yields of up to 85%.
[0089] The following three trinuclear mesogendiols are prepared in
accordance with the above reaction scheme:
1TABLE Trinuclear mesogendiols prepared by axeotropic
esterification 19 20 2a 21 2b 22 2c
[0090] Trinuclear mesogendiols in which the hydroquinone unit
carries one or more bulky groups are preferably prepared by a
different route. Examples of said bulky groups are tert-butyl or
aryl radicals. Trinuclear mesogendiols of this type are prepared in
accordance with reaction scheme 3, for example using
tert-butyl-hydroquinone (Galli et al., Polymer Bulletin (1989) 21,
563). 23
[0091] The phenolic hydroxyl group of 4-hydroxybenzoic acid is
protected using benzyl chloroformate. The 4-hydroxybenzoic acid
thus protected is subsequently reacted with thionyl chloride to
give the corresponding acid chloride. The reaction of the latter
with tert-butyl hydroquinone in the presence of triethylamine as
acid-scavenging base yields the hydroxy-protected diester. In a
final reaction step, the protective groups are removed by catalytic
hydrogenation over a palladium catalyst. The mesogendiols prepared
by this procedure were obtained in yields of up to 40%. The low
overall yield results from low yields in the preparation of the
benzyl-protected mesogendiols. Examples of trinuclear mesogendiols
which can be prepared in accordance with this reaction scheme are
listed in the table below.
2TABLE Trinuclear mesogendiols carrying bulky groups 24 25 2d 26 2e
27 2f
[0092] 3. Synthesis of Tetranuclear Mesogendiols
[0093] The reactions described above for the synthesis of
trinuclear mesogendiols can likewise be applied to tetranuclear
mesogendiols. The structure of the tetranuclear mesogendiols
differs from that of the trinuclear mesogendiols merely in that the
central part of the molecule does not consist of a hydroquinone
unit but of a binuclear aromatic diol component. The examples of
two tetranuclear mesogendiols which can be used according to the
invention are listed in the table below. The compounds were
prepared by azeotropic esterification in p-xylene using
p-toluenesulfonic acid as catalyst. Yields were up to 77%.
3TABLE Tetrafluclear mesogendiol-s prepared by azeotropic
esterification 28 29 3a 30 3b
[0094] B. Synthesis of Novel Liquid-Crystalline Tetraacrylates
[0095] Preferred liquid-crystalline tetraacrylates according to the
invention are obtainable via 3,4-di-(6-acryloyloxyhexyloxy)benzoic
acid. 3,4-Di-(6-acryloyloxyhexyloxy)benzoic acid is synthesized in
a conventional manner (Stohr, Dissertation, University of Bayreuth,
1996). The synthesis is depicted in reaction scheme 4 below: 31
[0096] In the first step of this synthesis, ethyl
3,4-dihydroxybenzoate is subjected to basic etherification with
6-chlorohexanol. The ethyl ester is subsequently hydrolyzed with
methanolic potassium hydroxide solution to isolate the free acid.
The latter was then esterified with acryloyl chloride in
1,4-dioxane using diethylaniline as base to scavenge the
hydrochloric acid that had been liberated. In a second step, the
acid is then converted into the acid chloride and reacted with
various mesogendiols. This second stage is depicted in reaction
scheme 5 below: 32 33
[0097] To this end, 3,4-di-(6-acryloyloxyhexyloxy)benzoic acid was
converted into the acid chloride using oxalyl chloride. Without
further purification, the latter was then reacted with the
respective mesogendiol in THF in a ratio of 2:1. Triethyl5 amine
was used as a base to bind the hydrochloric acid formed during
esterification. All tetraacrylates thus prepared were subsequently
purified by column chromatography. Tetraacrylate yields were
between 42% and 72%.
[0098] The structure of the tetraacrylates synthesized in
accordance with the above reaction scheme are summarized in the
following table.
4TABLE Tetraacrylates synthesized and their mesophase behavior 34
14a 35 14b 36 14c 37 14d
[0099] a) DSC, 2nd heating, inhibitor content: 2% by weight of
sulfur, heating rate 10 K/min
[0100] b) Polarization microscope
[0101] c) Cr=crystalline; N=nematic; I=isotropic
[0102] The phase behavior of the tetraacrylates was analyzed by
means of DSC and polarization microscopy. 2% by weight of sulfur
were added as inhibitor to prevent thermal polymerization during
the analysis. A nematic mesophase was detected for all four
tetra-acrylates. Of the tetraacrylates having a pentanuclear
mesogenic unit, 14a exhibits a nematic mesophase between
121.degree. C. and 127.degree. C. and 14b exhibits a nematic
mesophase between 107.degree. C. and 122.degree. C. The methyl
substitution on the mesogenic unit leads to a decrease both in
melting point and in clearing point compared to the unsubstituted
system 14a. The effect of the substituent on the melting point is
significantly stronger than the effect on the clearing point.
[0103] Of the tetraacrylates having a hexanuclear mesogenic unit,
14c exhibits a nematic mesophase between 123.degree. C. and
155.degree. C. The tetraacrylate 14d likewise shows nematic
behavior. In the case of this tetraacrylate, however, the nematic
mesophase cannot be detected in the DSC heating curve, whereas a
fluid mesophase between 132.degree. C. and 143.degree. C. is
observed under the polarization microscope. Only the DSC cooling
curve shows a mesophase having a clearly noticeable transition
between isotropic and nematic phase. The introduction of the two
methyl groups leads to a significant reduction in the phase width
compared to 14c. It is interesting that the melting point is
increased on introduction of two methyl groups, whereas the
introduction of one methyl group led to a decrease in the melting
point in the case of 14b. In the case of 14b and 14c, the DSC
measurements show additional transitions in the crystalline region.
These transitions were not analyzed any further.
[0104] On the basis of the specific instructions given above, the
person skilled in the art can carry out usual modifications of the
specific embodiments described to obtain further compounds
according to the invention.
[0105] The examples which follow illustrate the invention.
EXPERIMENTAL SECTION
[0106]
5 Apparatus and auxiliaries IR spectroscopy: BIO-RAD Digilab FTS-40
(FT IR) .sup.1H NMR spectroscopy: BRUKER AC 250 (250 MHz) .sup.13C
NMR spectroscopy: BRUKER AC 250 (62.5 MHz) DSC: PERKIN-ELMER DSC 7
Polarization microscopy: NIKON Diaphot with Mettler FP82 hot bench,
Mettler FP90 control unit
[0107] Chemicals and Solvents
[0108] Dioxane was dried by refluxing over potassium and was
distilled off under protective gas. Tetrahydrofuran was initially
refluxed over potassium hydroxide, distilled off, again refluxed
over potassium and finally distilled off under protective gas.
Methylene chloride was dried by refluxing over calcium hydride and
distilled off under protective gas. All other solvents were
distilled through packed columns and used without further drying.
Triethylamine was refluxed over potassium hydroxide and distilled
off under protective gas. Acryloyl chloride was purified by double
fractionated distillation under protective gas using
2,6-di-tert-butyl-p-cresol as stabilizer. All other chemicals used
were commercially available in sufficent purity and therefore used
without further purification.
Reference Example 1
Preparation of Mesogendiols
[0109] The following mesogendiols were prepared: 38
Reference Example 1.1
Preparation of 2,2'-dimethyl-4,4'-dihydroxybiphenyl (1)
[0110] a) 4-Chloro-3-methylphenyl Acetate
[0111] 43.0 g (0.30 mol) of 4-chloro-3-methylphenol, 34 ml (0.36
mol) of acetic anhydride and a few drops of concentrated sulfuric
acid were stirred for 2 h at 60.degree. C. in a 250 ml flask
equipped with a reflux condenser. The reaction mixture was cooled
to room temperature, poured into 200 ml of water and stirred for 1
h at room temperature. The mixture was then extracted with 400 ml
of diethyl ether. The organic phase was dried over magnesium
sulfate and the ether was distilled off. The raw product is
subsequently distilled under reduced pressure (b.p. 65-68.degree.
C., 20 mbar).
[0112] Yield: 52.5 g (95% of theory) in the form of a colorless
liquid
[0113] Characterization:
[0114] IR (film): .nu. (cm.sup.-1): 3050, 2985, 2957, 2923, 1770,
1611, 1581, 1479, 1370, 1053, 1017, 899, 814, 705, 684.
[0115] .sup.1H NMR (CDCl.sub.3): .delta. (ppm): 7.32 (d, 1H, ortho
to --Cl), 6.96 (d, 1H, ortho to --CH.sub.3), 6.87 (dd, 1H, para to
--CH.sub.3), 2.35 (s, 3H, --OOC--CH.sub.3), 2.27 (s, 3H,
--CH.sub.3).
[0116] b) 2,2'-Dimethyl-4,4'-dihydroxybiphenyl
[0117] 2.08 g (0.016 mol) of nickel dichloride, 20.9 g (0.080 mol)
of triphenylphosphane (PPh.sub.3), 30.1 g (0.460 mol) of zinc
powder, 2.51 g (0.016 mol) of 2,2'-bipyridine (bpy) and 160 ml of
dimethylacetamide (DMAc) are introduced into a 500 ml flask
equipped with a reflux condenser. The reaction mixture is heated to
65.degree. C. 52.5 g (0.285 mol) of 4-chloro-3-methylphenyl acetate
are added, and the reaction mixture is stirred for 4 h at
70.degree. C. The reaction mixture is cooled to room temperature,
filtered, poured onto 500 ml of a 2.5 molar sodium hydroxide
solution and stirred overnight. The mixture is washed with 300 ml
of diethyl ether, and the aqueous phase is acidified with
concentrated hydrochloric acid (pH=1). The aqueous phase is then
extracted with 800 ml of diethyl ether and the diethyl ether is
distilled off. The raw product is distilled under reduced pressure
(b.p. 167-170.degree. C., 0.01 mbar) and subsequently
recrystallized twice from toluene.
[0118] Yield: 18.5 g (61% of theory) in the form of a white
solid
[0119] Characterization:
[0120] IR (KBr): .nu. (cm.sup.-1): 3328, 3023, 2921, 1606, 1583,
1488, 1452, 1233, 1160, 814.
[0121] .sup.1H NMR (DMSO): .delta. (ppm): 9.19 (s, 2H, OH), 6.79
(d, 2H, meta to --CH.sub.3), 6.65 (d, 2H, ortho to --CH.sub.3),
6.57 (dd, 2H, para to --CH.sub.3), 1.89 (s, 6H, --CH.sub.3).
[0122] .sup.13C NMR (DMSO): .delta. (ppm): 156.26, 136.90, 132.07,
130.69, 116.50, 112.66 (aromatic), 19.98 (--CH.sub.3).
[0123] Melting point: 137-138.degree. C.
Reference Example 1.2
Preparation of Mesogendiols by Azeotropic Esterification
[0124] A) General procedure: The respective 4-hydroxybenzoic acid
and the respective aromatic diol are introduced together with
p-toluenesulfonic acid in p-xylene into a flask equipped with a
water separator and refluxed for 24 h. After water separation is
complete, the reaction mixture is cooled to room temperature and
the raw product is filtered off.
[0125] B) Compounds prepared in accordance with the general
procedure:
[0126] a) 1,4-Phenylene-bis-(4-hydroxy)benzoate (2a)
[0127] Purification: The raw product is suspended in 100 ml of
ethanol, stirred for several hours at room temperature and then
separated by filtration. The product is obtained in the form of a
white solid.
6 Batch: 3.30 g (0.03 mol) of hydroquinone 8.29 g (0.06 mol) of
4-hydroxybenzoic acid 0.60 g (0.003 mol) of p-toluenesulfonic acid
150 ml of p-xylene
[0128] Yield: 8.50 g (81% of theory) in the form of a white
solid
[0129] Characterization:
[0130] IR (KBr): .nu. (cm.sup.-1): 3380, 3069, 1693, 1611, 1593,
1514, 1286, 1166, 1081, 901, 847.
[0131] .sup.1H NMR (DMSO): .delta. (ppm): 10.54 (s, 2H, --OH), 8.00
(d, 4H, aromatic), 7.31 (s, 4H, aromatic), 6.94 (d, 4H,
aromatic).
[0132] .sup.13C NMR (DMSO): .delta. (ppm): 164.65 (--COO--),
162.699, 148.39, 132.52, 123.19, 119.49, 115.86 (aromatic).
[0133] Decomposition (Ton): 294.degree. C.
[0134] b) 2-Methyl-1,4-phenylene-bis-(4-hydroxy)benzoate (2b)
[0135] Purification: The raw product is slurried in 100 ml of
diethyl ether, stirred for several hours at room temperature and
then separated by filtration. The product is obtained in the form
of a white solid.
7 Batch: 3.72 g (0.03 mol) of 2-methylhydroquinone 8.29 g (0.06
mol) of 4-hydroxybenzoic acid 0.60 g (0.003 mol) of
p-toluenesulfonic acid 150 ml of p-xylene
[0136] Yield: 9.31 g (85% of theory) in the form of a white
solid
[0137] Characterization:
[0138] IR (KBr): .nu. (cm.sup.-1): 3392, 3077, 2928, 1697, 1609,
1594, 1513, 1281, 1161, 1078, 847.
[0139] .sup.1H NMR (DMSO): .delta. (ppm): 10.53 (s, 2H, --OH), 8.00
(t, 4H, aromatic), 7.17 (m, 3H, aromatic), 6.94 (dd, 4H, aromatic),
2.15 (s, 3H, Ar--CH.sub.3).
[0140] .sup.13C NMR (DMSO): .delta. (ppm): 164.65, 164.32
(--COO--), 163.03, 162.96, 148.33, 146.98, 132.48, 131.66, 124.37,
123.34, 120.60, 119.51, 119.31, 115.85 (aromatic), 16.01
(--CH.sub.3).
[0141] Decomposition (Ton): 276.degree. C.
[0142] c) 2,3,5-Trimethyl-1,4-phenylene-bis-(4-hydroxy)benzoate
(2c)
[0143] Purification: The raw product is slurried in 100 ml of
diethyl ether, stirred for several hours at room temperature and
then separated by filtration. The raw product is then
recrystallized from 1 000 ml of methanol. The product is obtained
in the form of a white solid.
8 Batch: 4.56 g (0.03 mol) of 2,3,5-trimethylhydroquinone 8.29 g
(0.06 mol) of 4-hydroxybenzoic acid 0.60 g (0.003 mol) of
p-toluenesulfonic acid 150 ml of p-xylene
[0144] Yield: 6.65 g (57% of theory) in the form of a white
solid
[0145] Characterization:
[0146] IR (KBr): .nu. (cm.sup.-1): 3414, 1705, 1606, 1588, 1512,
1273, 1162, 1087, 848.
[0147] .sup.1H NMR (DMSO): .delta. (ppm): 10.54 (s, 2H, --OH), 8.01
(t, 4H, aromatic), 6.98 (s, 1H, aromatic), 6.94 (dd, 4H, aromatic),
2.06 (s, 3H, Ar--CH.sub.3), 2.03 (s, 3H, Ar--CH.sub.3), 2.02 (s,
3H, Ar--CH.sub.3).
[0148] .sup.13C NMR (DMSO): .delta. (ppm): 164.43, 163.94
(--COO--), 163.04, 151.80, 146.57, 145.68, 132.41, 130.30, 128.39,
127.57, 121.72, 119.36, 119.04, 115.91 (aromatic), 16.02, 13.11,
12.74 (Ar--CH.sub.3).
[0149] Decomposition (T.sub.on): 298.degree. C.
[0150] d) 4,4'-Biphenylene-bis-(4-hydroxy)benzoate (3a)
[0151] Purification: Recrystallization from 1500 ml of
cyclohexanone.
9 Batch: 8.75 g (0.047 mol) of 4,4'-dihydroxybiphenyl 12.98 g
(0.094 mol) of 4-hydroxybenzoic acid 2.00 g (0.01 mol) of
p-toluenesulfonic acid 250 ml of p-xylene
[0152] Yield: 15.40 g (77% of theory)
[0153] Characterization:
[0154] IR (KBr): .nu. (cm.sup.-1): 3415, 1703, 1603, 1587, 1511,
1279, 1197, 1160, 1079, 1004, 851.
[0155] .sup.1H NMR (DMSO): .delta. (ppm): 10.52 (s, 2H, --OH), 8.00
(d, 4H, aromatic), 7.74 (d, 4H, aromatic), 7.32 (d, 4H, aromatic),
6.93 (d, 4H, aromatic).
[0156] .sup.13C NMR (DMSO): .delta. (ppm): 164.57 (--COO--),
162.95, 150.56, 137.14, 132.48, 127.95, 122.72, 119.51, 115.84
(aromatic).
[0157] Decomposition (T.sub.on): 320.degree. C.
[0158] e) 2,2'-Dimethyl-4,4'-biphenylene-bis-(4-hydroxy)benzoate
(3b)
[0159] Purification: Recrystallization from 700 ml of
1,4-dioxane
10 Batch: 9.43 g (0.044 mol) of 2,2'-dimethyl-4,4'-dihydro- xy-
biphenyl 12.19 g (0.088 mol) of 4-hydroxybenzoic acid 2.00 g (0.01
mol) of p-toluenesulfonic acid 250 ml of p-xylene
[0160] Yield: 14.73 g (74% of theory)
[0161] Characterization:
[0162] IR (KBr): .nu. (cm.sup.-1): 3410, 1700, 1607, 1592, 1513,
1449, 1279, 1221, 1154, 1086, 1007, 850.
[0163] .sup.1H NMR (DMSO): .delta. (ppm): 10.52 (s, 2H, --OH), 7.99
(d, 4H, aromatic), 7.15 (m, 6H, aromatic), 6.93 (d, 4H, aromatic),
2.04 (s, 6H, Ar--CH.sub.3).
[0164] .sup.13C NMR (DMSO): .delta. (ppm): 164.53 (--COO--),
162.86, 150.07, 137.86, 137.20, 132.37, 130.32, 123.29, 119.58,
115.80 (aromatic), 19.72 (Ar--CH.sub.3).
[0165] Decomposition (T.sub.on): 242.degree. C.
Reference Example 1.3
Preparation of Mesogendiols via Protected 4-hydroxybenzoic
Acids
[0166] A) General Procedure
[0167] i) Introduction of a Protective Group at the Hydroxyl
Function of the 4-hydroxybenzoic Acid
[0168] The respective 4-hydroxybenzoic acid is dissolved in 1 M
aqueous sodium hydroxide solution. The benzyl chloroformate is
added dropwise at 0.degree. C. The reaction mixture is stirred for
2 h and then poured into 2 M hydrochloric acid. The resulting
precipitate is separated by filtration and recrystallized.
[0169] ii) Preparation of the Hydroxy-Protected Mesogendiol
[0170] The protected 4-hydroxybenzoic acid is dissolved in
1,2-dichloroethane. Thionyl chloride is added and the solution is
refluxed for 2 h. The solvent and unreacted thionyl chloride are
distilled off under reduced pressure. The resulting carbonyl
chloride is dissolved in 1,2-dichloroethane and added dropwise to a
solution of an aromatic diol and triethylamine in
1,2-dichloroethane. The reaction mixture is refluxed for 2 h,
cooled to room temperature and filtered. 1,2-Dichloroethane is
distilled off under reduced pressure, and the residue is taken up
in chloroform and washed with water. The organic phase is dried
over Na.sub.2SO.sub.4. The chloroform is then distilled off and the
raw product is purified by recrystallization.
[0171] iii) Libration of the Mesogendiol by Catalytic Removal of
the Protective Groups
[0172] The protected mesogendiol is added to tetrahydrofuran
together with palladium on activated carbon (5%). The reaction
mixture is saturated with hydrogen and then stirred under a
hydrogen atmosphere at 40.degree. C. overnight. The reaction
mixture is then filtered and the THF is distilled off.
[0173] B) Compounds Prepared According to the General
Procedure:
[0174] a) Benzyloxy-4-hydroxybenzoic Acid
[0175] Purification: Recrystallization from 1200 ml acetone/water
1:1
11 Batch: 20.00 g (0.143 mol) of 4-hydroxybenzoic acid 29.6 g
(0.173 mol) of benzyl chloroformate 300 ml of 1 M sodium hydroxide
solution 500 ml of 2 M hydrochloric acid
[0176] Yield: 29.3 g (75% of theory) in the form of a white
solid
[0177] Characterization:
[0178] IR (KBr): .nu. (cm.sup.-1): 3036, 2874, 2673, 2544, 1754,
1696, 1608, 1428, 1163, 957, 853.
[0179] .sup.1H NMR (DMSO): .delta. (ppm): 13.10 (s, 1H, --COOH),
8.00 (d, 2H, aromatic),7.40 (m, 7H, aromatic), 5.29 (s, 2H,
Ar--CH.sub.2--OCOO--).
[0180] b) Benzyloxy-4-hydroxyvanillic Acid
[0181] Purification: Recrystallization from a mixture of 450 ml of
water and 250 ml of acetone
12 Batch: 18.90 g (0.11 mol) of vanillic acid 25.60 g (0.15 mol) of
benzyl chloroformate 400 ml of 1 M sodium hydroxide solution 1000
ml of 2 M hydrochloric acid
[0182] Yield: 20.3 g (61% of theory)
[0183] Characterization:
[0184] IR (KBr): .nu. (cm.sup.-1): 2963, 2619, 1780, 1761, 1686,
1608, 1427, 1241, 1182, 1124, 1029.
[0185] .sup.1H NMR (DMSO): .delta. (ppm): 13.10 (s, 1H, --COOH),
7.58 (m, 2H, aromatic), 7.38 (m, 6H, aromatic), 5.27 (s 2H,
Ar--CH.sub.2--OCOO--), 3.81 (s, 3H, Ar--OCH.sub.3).
[0186] c)
2-tert-Butyl-1,4-phenylene-bis-(4-benzylcarbonato)benzoate
[0187] Purification: Recrystallization from 1 000 ml of
cyclohexane
13 Batch: 35.52 g (0.13 mol) of benzyloxy-4-hydroxybenzoic acid 12
ml (0.17 mol) of thionyl chloride 150 ml of 1,2-dichloroethane 9.72
g (0.06 mol) of tert-butylhydroquinone 37 ml (0.26 mol) of
triethylamine 200 ml of 1,2-dichloroethane
[0188] Yield: 17.2 g (43% of theory) in the form of a white
solid
[0189] Characterization:
[0190] IR (KBr): .nu. (cm.sup.-1): 3037, 2952, 2869, 1759, 1736,
1606, 1506, 1390, 1258, 1160, 1073, 727.
[0191] .sup.1H NMR (CDCl.sub.3): .delta. (ppm): 8.25 (m, 4H,
aromatic), 7.3 (m, 17H, aromatic), 5.30 (s, 4H,
Ar--CH.sub.2--OCOO--), 1.40 (s, 9H, Ar--C(CH.sub.3).sub.3).
[0192] d)
2-Phenyl-1,4-phenylene-bis-(4-benzylcarbonato)benzoate
[0193] Purification: Recrystallization from 1 000 ml of
cyclohexane
14 Batch: 29.3 g (0.11 mol) of benzyloxy-4-hydroxybenzoic acid 12
ml (0.17 mol) of thionyl chloride 150 ml of 1,2-dichloroethane 7.91
g (0.043 mol) of phenylhydroquinone 31 ml (0.22 mol) of
triethylamine 200 ml of 1,2-dichloroethane
[0194] Yield: 16.0 g (54% of theory) in the form of a white
solid
[0195] Characterization:
[0196] IR (KBr): .nu. (cm.sup.-1): 2960, 2923, 1758, 1737, 1605,
1508, 1486, 1411, 1381, 1255, 1162, 1078, 1016.
[0197] .sup.1H NMR (CDCl.sub.3): .delta. (ppm): 8.24 (dd, 2H,
aromatic), 8.04 (dd, 2H, aromatic), 7.34 (m, 23H, aromatic), 5.29
(s, 2H, Ar--CH.sub.2--OCOO--), 5.27 (s, 2H,
--CH.sub.2--OCOO--).
[0198] e)
2-tert-Butyl-1,4-phenylene-bis-(3-methoxy-4-benzylcarbonato)-ben-
zoate
[0199] Purification: Reprecipitated in ice water from a solution in
THF
15 Batch: 12.04 g (0.04 mol) of benzyloxyvanillic acid 7.3 ml (0.1
mol) of thionyl chloride 70 ml of 1,2-dichloroethane 2.66 g (0.016
mol) of tert-butylhydroquinone 11.4 ml (0.08 mol) of triethylamine
130 ml of 1,2-dichloroethane
[0200] Yield: 5.98 g (51% of theory)
[0201] Characterization:
[0202] IR (KBr): .nu. (cm.sup.-1): 2968, 1768, 1738, 1607, 1508,
1413, 1288, 1248, 1166, 1083, 1027, 741.
[0203] .sup.1H NMR (CDCl.sub.3): .delta. (ppm): 7.85 (m, 4H,
aromatic), 7.38 (m, 14H, aromatic), 7.14 (s, 1H, aromatic), 5.30
(s, 4H, Ar--CH.sub.2--OCOO--), 3.89 (s, 6H, Ar--OCH.sub.3), 1.39
(s, 9H, Ar--C(CH.sub.3).sub.3).
[0204] f) 2-tert-Butyl-1,4-phenylene-bis-(4-hydroxy)benzoate
(2d)
16 Batch: 22.6 g (0.033 mol) of 2-tert-butyl-1,4-phenylene-
bis-(4-benzylcarbonato)-benzoate 2.5 g of palladium on activated
carbon (5%) 200 ml of THF
[0205] Yield: 12.0 g (89% of theory) in the form of a white
solid
[0206] Characterization:
[0207] IR (KBr): .nu. (cm.sup.-1): 3389, 2969, 1700, 1608, 1591,
1514, 1281, 160, 1079, 851, 766.
[0208] .sup.1H NMR (DMSO): .delta. (ppm): 10.54 (s, 2H, --OH), 8.00
(dd, 4H, aromatic), 7.19 (d, 2H, aromatic), 6.94, (t, 5H,
aromatic), 1.30 (s, 9H, Ar--C(CH.sub.3).sub.3).
[0209] .sup.13C NMR (DMSO): .delta. (ppm): 164.51, 164.41
(--COO--), 162.82, 162.68, 147.85, 146.38, 142.30, 132.23, 125.41,
120.38, 119.45, 119.32, 115.41, 115.57 (aromatic), 34.30
(Ar--C(CH.sub.3).sub.3), 29.80 (Ar--C(CH.sub.3).sub.3).
[0210] Decomposition (T.sub.on): 288.degree. C.
[0211] g) 2-Phenyl-1,4-phenylene-bis-(4-hydroxy)benzoate (2e)
17 Batch: 15.9 g (0.023 mol) of 2-phenyl-1,4-phenylene-bis-
(4-benzylcarbonato) benzoate 2.5 g of palladium on activated carbon
(5%) 200 ml of THF
[0212] Yield: 9.5 g (96% of theory) in the form of a white
solid
[0213] Characterization:
[0214] IR (KBr): .nu. (cm.sup.-1): 3392, 3064, 1700, 1608, 1590,
1513, 1482, 1278, 1160, 1079, 852.
[0215] .sup.1H NMR (DMSO): .delta. (ppm): 10.51 (s, 2H, --OH), 8.00
(d, 4H, aromatic), 7.85 (d, 2H, aromatic), 7.33 (m, 8H, aromatic),
6.93, (d, 2H, aromatic), 6.85 (d, 2H, aromatic).
[0216] .sup.13C NMR (DMSO): .delta. (ppm): 164.36, 164.25
(--COO--), 162.76, 162.70, 148.47, 145.05, 136.13, 135.25, 132.31,
132.15, 128.61, 128.38, 127.82, 124.55, 123.71, 122.08, 119.21,
119.01, 115.60 (aromatic).
[0217] Decomposition (T.sub.on): 290.degree. C.
[0218] h)
2-tert-Butyl-1,4-phenylene-bis-(3-methoxy-4-hydroxy)benzoate
(2f)
[0219] Purification: Reprecipitated in water from isopropanol
18 Batch: 11.45 g (0.016 mol) of 2-tert-butyl-1,4-phenylene- -
bis-(3-methoxy-4-benzyl- carbonato)benzoate 1 g of palladium on
activated carbon (5%) 100 ml of THF
[0220] Yield: 4.7 g (63% of theory) in the form of a yellowish
solid
[0221] Characterization:
[0222] IR (KBr): .nu. (cm.sup.-1): 3406, 2965, 2861, 1727, 1596,
1515, 1430, 1284, 1208, 1167, 1076, 870.
[0223] .sup.1H NMR (CDCl.sub.3): .delta. (ppm): 7.85 (m, 2H,
aromatic), 7.70 (dd, 1H, aromatic), 7.13 (m, 4H, aromatic), 6.17,
(d, 2H, aromatic), 3.99 (s, 6H, Ar--OCH.sub.3), 1.39 (s, 9H,
Ar--C(CH.sub.3).sub.3).
[0224] .sup.13C NMR (CDCl.sub.3): .delta. (ppm): 165.04 (--COO--),
150.77, 150.68, 148.16, 146.81, 146.44, 146.33, 142.85, 124.98,
121.59, 121.43, 120.57, 120.00, 114.43, 114.29, 112.31, 112.18
(aromatic), 56.14 (Ar--OCH.sub.3), 34.67 (Ar--C(CH.sub.3).sub.3),
30.06 (Ar--C(CH.sub.3).sub.3).
[0225] Melting point: 116.degree. C.
Reference Example 2
Preparation of Crosslinkable Spacer Units
3,4-di-(6-acryloyloxyhexyloxy)be- nzoic Acid
[0226] 39
[0227] a) 3,4-Di-(6-hydroxyhexyloxy)benzoic Acid
[0228] 10.93 g (0.06 mol) of ethyl 3,4-dihydroxybenzoate were added
to 200 ml of 2-butanone. 5.3 g (0.133 mol) of sodium hydroxide,
19.9 g (0.133 mol) of sodium iodide and 17.74 ml (0.133 mol) of
6-chlorohexanol are added and the reaction mixture is stirred for
20 h at 60.degree. C. The 2-butanone is then distilled off. The
residue is taken up in 300 ml of 0.4 M sodium hydroxide solution
and extracted four times with 100 ml of diethyl ether. The ether
phases are combined and concentrated on a rotary evaporator. The
residue is dissolved in 200 ml of methanol. 60 ml of 4.5 M
potassium hydroxide solution are added and the reaction mixture is
refluxed for 20 h. The reaction mixture is concentrated on a rotary
evaporator and the residue is taken up in 200 ml of 0.4 M sodium
hydroxide solution and washed three times with 100 ml of diethyl
ether. The aqueous phase is then acidified with a concentrated
hydrochloric acid (pH=1). The product which has precipitated is
separated by filtration and recrystallized from 500 ml of
water.
[0229] Yield: 14.3 g (67% of theory) in the form of a white
solid
[0230] Characterization:
[0231] IR (KBr): .nu. (cm.sup.-1): 3327, 2933, 2852, 1670, 1586,
1517, 1442, 1278, 1227, 1141, 869.
[0232] .sup.1H NMR (DMSO): .delta. (ppm): 12.59 (s, 1H, --COOH),
7.51 (dd, 1H, aromatic), 7.41 (d, 1H, aromatic), 7.01 (d, 1H,
aromatic), 4.33 (s, 2H, --OH), 3.97 (m, 4H, Ar--O--CH.sub.2--),
3.40 (m, 4H, --CH.sub.2--OH), 1.71 (m, 4H, alkoxy-CH.sub.2), 1.38
(m, 12H, alkoxy-CH.sub.2).
[0233] Melting point: 133-135.degree. C.
[0234] b) 3,4-Di-(6-acryloyloxyhexyloxy)benzoic Acid
[0235] 13.6 g (0.04 mol) of 3,4-di-(6-hydroxyhexyloxy)benzoic acid,
9.6 ml (0.06 mol) of N,N-diethylaniline and 100 mg of
2,6-di-tert-butyl-p-cresol as stabilizer are added to 150 ml of
1,4-dioxane and heated to 60.degree. C. At 60.degree. C., 6.9 ml
(0.085 mol) of acryloyl chloride are added slowly such that the
reaction temperature does not exceed 65.degree. C. The reaction
mixture is stirred for 2.5 h at 60.degree. C. The solution is
cooled to room temperature and poured onto ice water with stirring.
A precipitate of 3,4-di-(6-acryloyloxyhexyloxy)benzoic acid is
obtained which is separated by filtration, dried and recrystallized
from 300 ml of isopropanol.
[0236] Yield: 13.1 g (71% of theory) in the form of a white
solid
[0237] Characterization:
[0238] IR (KBr): .nu. (cm.sup.-1): 3086, 2940, 2854, 1723, 1669,
1596, 1441, 1278, 1196, 1042, 868.
[0239] .sup.1H NMR (DMSO): .delta. (ppm): 12.55 (s, 1H, --COOH),
7.51 (dd, 1H, aromatic), 7.41 (d, 1H, aromatic), 7.01 (d, 1H,
aromatic), 6.29 (dd, 2H, --CH.dbd.CH.sub.2 trans), 6.14 (dd, 2H,
--CH.dbd.CH.sub.2), 5.90 (dd, 2H, --CH.dbd.CH.sub.2 cis), 4.03 (m,
8H, Ar--O--CH.sub.2-- and --COO--CH.sub.2--), 1.72 (m, 4H,
alkoxy-CH.sub.2), 1.61 (m, 4H, alkoxy-CH.sub.2), 1.41 (m, 8H,
alkoxy-CH.sub.2).
[0240] .sup.13C NMR (DMSO): .delta. (ppm): 170.27 (--COOH), 167.29,
165.68 (--COO--CH.sub.2), 152.65, 148.06, 131.43, 128.58, 123.48,
123.08, 114.03, 112.48 (aromatic and --CH.dbd.CH.sub.2), 68.50
(Ar--O--CH.sub.2--), 68.36 (--COO--CH.sub.2--), 28.70, 28.65,
28.27, 25.66, 25.35, 25.27 (alkoxy-CH.sub.2).
[0241] Melting point: 90-92.degree. C.
Example 1
Preparation of Tetraacrylates
[0242] The following tetraacrylates were prepared:
[0243] Tetraacrylates: 40
[0244] A) General Procedure for Preparing Tetraacrylates Using Acid
Chloride
[0245] i) Preparation of the Acid Chloride
[0246] The respective spacer-carrying hydroxybenzoic acid is
suspended in methylene chloride. Oxalyl chloride is slowly added in
a molar excess of about 8-10 times with ice cooling. The reaction
mixture is stirred at room temperature until gas evolution is no
longer observed. A clear solution is obtained from which the
methylene chloride and unreacted oxalyl chloride are distilled off
under reduced pressure. The remaining acid chloride was reacted
further without further purification.
[0247] ii) Reaction of the Acid Chloride with Mesogendiols
[0248] The respective mesogendiol is added to THF together with
triethylamine and 2,6-di-tert-butyl-p-cresol as stabilizer (only in
the case of acrylates). The acid chloride is dissolved in THF and
added with ice cooling. The mixture is then stirred for 24 h at
room temperature. The mixture is then filtered and concentrated on
a rotary evaporator. The residue is taken up in chloroform and
extracted three times with water. The solvent is then evaporated,
the raw product obtained is dried under reduced pressure and
purified by recrystallization or by column chromatography.
[0249] B) Tetraacrylates Synthesized in Accordance with the General
Procedure
[0250] a) Tetraacrylate 14a
[0251] Purification: Column chromatography (chloroform/ethyl
acetate 40:1)
19 Batch: 3.55 g (7.68 .multidot. 10.sup.-3 mol) of
3,4-di-[6-(acryloyloxy- hexyloxy)]benzoic acid 6 ml (0.070 mol) of
oxalyl chloride 40 ml of methylene chloride 1.21 g (3.45 .multidot.
10.sup.-3 mol) of 1,4-phenylene-bis- (4-hydroxy)benzoate 2 ml
(0.014 mol) of triethylamine 100 ml of THF 50 mg of
2,6-di-tert-butyl-p-cresol
[0252] Yield: 1.84 g (43% of theory) in the form of a white
solid
[0253] Characterization:
[0254] IR (KBr): .nu. (cm.sup.-1): 2939, 2855, 1735, 1599, 1508,
1410, 1270, 1204, 1160, 1065, 1016, 811.
[0255] .sup.1H NMR (CDCl.sub.3): .delta. (ppm): 8.23 (d, 4H,
aromatic), 7.78 (dd, 2H, aromatic), 7.60 (d, 2H, aromatic), 7.31
(d, 2H, aromatic), 7.19 (s, 4H, aromatic), 6.88 (d, 4H, aromatic),
6.34 (dd, 4H, --CH.dbd.CH.sub.2 trans), 6.06 (dd, 4H,
--CH.dbd.CH.sub.2), 5.75 (dd, 4H, --CH.dbd.CH.sub.2 cis), 4.08 (m,
16H, --COO--CH.sub.2-- and Ar--O--CH.sub.2--), 1.84 (m, 8H,
alkoxy-CH.sub.2), 1.66 (m, 8H, alkoxy-CH.sub.2), 1.45 (m, 16H,
alkoxy-CH.sub.2).
[0256] .sup.13C NMR (CDCl.sub.3): .delta. (ppm): 166.24, 164.36,
164.31 (--COO--), 155.42, 153.95, 148.59, 148.35, 131.81, 130.51,
128.52, 126.72, 124.60, 122.63, 122.12, 121.02, 114.53, 111.90
(aromatic and --CH.dbd.CH.sub.2), 69.05, 68.80 (Ar--O--CH.sub.2--),
64.40 (--COO--CH.sub.2--), 28.88, 28.53, 26.56, 25.64, 25.31
(alkoxy-CH.sub.2).
[0257] Thermal behavior: Cr 121 N 127 I (DSC, 2nd heating, heating
rate 10 K/min, 2% by weight of sulfur).
[0258] b) Tetraacrylate 14b
[0259] Purification: Column chromatography (chloroform/ethyl
acetate 40:1)
20 Batch: 2.00 g (4.32 .multidot. 10.sup.-3 mol) of
3,4-di-[6-(acryloyloxy- hexyloxy)]benzoic acid 3.5 ml (0.041 mol)
of oxalyl chloride 30 ml of methylene chloride 0.71 g (1.94
.multidot. 10.sup.-3 mol) of 2-methyl-1,4-phenylene-bis-
(4-hydroxy)benzoate 1 ml (0.007 mol) of triethylamine 80 ml of THF
50 mg of 2,6-di-tert-butyl-p-cresol
[0260] Yield: 1.65 g (68% of theory) in the form of a white
solid
[0261] Characterization:
[0262] IR (KBr): .nu. (cm.sup.-1): 2939, 2861, 1731, 1598, 1519,
1430, 1410, 1202, 1158, 1068, 1015, 811.
[0263] .sup.1H NMR (CDCl.sub.3): .delta. (ppm): 8.29 (m, 4H,
aromatic), 7.84 (dd, 2H, aromatic), 7.67 (d, 2H, aromatic), 7.38
(d, 3H, aromatic), 7.20 (m, 4H, aromatic), 6.95 (d, 2H, aromatic),
6.40 (dd, 4H, --CH.dbd.CH.sub.2 trans), 6.12 (dd, 4H,
--CH.dbd.CH.sub.2), 5.81 (dd, 4H, --CH.dbd.CH.sub.2 cis), 4.14 (m,
16H, --COO--CH.sub.2-- and Ar--O--CH.sub.2--), 2.28 (s, 3H,
Ar--CH.sub.3), 1.88 (m, 8H, alkoxy-CH.sub.2), 1.72 (m, 8H,
alkoxy-CH.sub.2), 1.52 (m, 16H, alkoxy-CH.sub.2).
[0264] .sup.13C NMR (CDCl.sub.3): .delta. (ppm): 166.16, 164.32,
163.93 (--COO--), 155.36, 155.32, 153.91, 148.54, 148.30, 146.93,
131.74, 131.71, 130.45, 130.42, 128.48, 126.75, 126.58, 124.55,
124.02, 122.81, 122.11, 122.03, 120.96, 119.96, 114.47, 111.86
(aromatic and --CH.dbd.CH.sub.2), 68.99, 68.74 (Ar--O--CH.sub.2--),
64.37, 64.34 (--COO--CH.sub.2--), 28.92, 28.81, 28.48, 25.60
(alkoxy-CH.sub.2), 16.36 (Ar--CH.sub.3).
[0265] Thermal behavior: Cr 107 N 122 I (DSC, 2nd heating, heating
rate 10 K/min, 2% by weight of sulfur).
[0266] c) Tetraacrylate 14c
[0267] Purification: Column chromatography (chloroform/ethyl
acetate 40:1)
21 Batch: 3.04 g (6.57 .multidot. 10.sup.-3 mol) of
3,4-di-[6-(acryloyloxy- hexyloxy)]benzoic acid 5 ml (0.058 mol) of
oxalyl chloride 40 ml of methylene chloride 1.26 g (2.95 .multidot.
10.sup.-3 mol) of 4,4'-biphenylene-bis- (4-hydroxy)benzoate 1.5 ml
(0.01 mol) of triethylamine 100 ml of THF 50 mg of
2,6-di-tert-butyl-p-cresol
[0268] Yield: 2.79 g (72% of theory) in the form of a white
solid
[0269] Characterization:
[0270] IR (KBr): .nu. (cm.sup.-1): 2937, 2866, 1733, 1597, 1431,
1270, 1193, 1161, 1069, 1005, 879.
[0271] .sup.1H NMR (CDCl.sub.3): .delta. (ppm): 8.31 (d, 4H,
aromatic), 7.84 (dd, 2H, aromatic), 7.66 (m, 6H, aromatic), 7.36
(m, 6H, aromatic), 6.94 (d, 4H, aromatic), 6.40 (dd, 4H,
--CH.dbd.CH.sub.2 trans), 6.12 (dd, 4H, --CH.dbd.CH.sub.2), 5.81
(dd, 4H, --CH.dbd.CH.sub.2 cis), 4.15 (m, 16H, --COO--CH.sub.2--
and Ar--O--CH.sub.2--), 1.90 (m, 8H, alkoxy-CH.sub.2), 1.73 (m, 8H,
alkoxy-CH.sub.2), 1.52 (m, 16H, alkoxy-CH.sub.2).
[0272] .sup.13C NMR (CDCl.sub.3): .delta. (ppm): 166.26, 164.47,
164.38 (--COO--) 155.40, 153.95, 150.37, 148.61, 138.23, 131.83,
130.68, 128.52, 128.23, 126.84, 124.60, 122.12, 122.03, 121.03,
114.53, 111.92 (aromatic and --CH.dbd.CH.sub.2), 69.07, 68.81
(Ar--O--CH.sub.2--), 64.46, 64.41 (--COO--CH.sub.2--), 28.99,
28.87, 28.54, 25.60 (alkoxy-CH.sub.2).
[0273] Thermal behavior: Cr 123 N 155 I (DSC, 2nd heating, heating
rate 10 K/min, 2% by weight of sulfur).
[0274] d) Tetraacrylate 14d
[0275] Purification: Column chromatography (chloroform/ethyl
acetate 40:1)
22 Batch: 3.05 g (6.60 .multidot. 10.sup.-3 mol) of
3,4-di-[6-(acryloyloxy- hexyloxy)]benzoic acid 5.5 ml (0.064 mol)
of oxalyl chloride 40 ml of methylene chloride 1.34 g (2.95
.multidot. 10.sup.-3 mol) of 2,2'-dimethyl- 4,4'-biphenylene-bis-
(4-hydroxy)benzoate 1.5 ml (0.01 mol) of triethylamine 100 ml of
THF 50 mg of 2,6-di-tert-butyl-p-cresol
[0276] Yield: 1.66 g (42% of theory) in the form of a white
solid
[0277] Characterization:
[0278] IR (KBr): .nu. (cm.sup.-1): 2936, 2861, 1727, 1596, 1516,
1430, 1274, 1194, 1064, 1010, 816.
[0279] .sup.1H NMR (CDCl.sub.3): .delta. (ppm): 8.31 (d, 4H,
aromatic), 7.85 (dd, 2H, aromatic), 7.67 (d, 2H, aromatic), 7.38
(d, 4H, aromatic), 7.16 (m, 6H, aromatic), 6.95 (d, 2H, aromatic),
6.40 (dd, 4H, --CH.dbd.CH.sub.2 trans), 6.12 (dd, 4H,
--CH.dbd.CH.sub.2), 5.83 (dd, 4H, --CH.dbd.CH.sub.2 cis), 4.13 (m,
16H, --COO--CH.sub.2-- and Ar--O--CH.sub.2--), 2.13 (s, 6H,
aromatic), 1.91 (m, 8H, alkoxy-CH.sub.2), 1.73 (m, 8H,
alkoxy-CH.sub.2), 1.50 (m, 16H, alkoxy-CH.sub.2).
[0280] .sup.13C NMR (CDCl.sub.3): .delta. (ppm): 166.23, 164.54,
164.38 (--COO--) 155.33, 153.94, 150.03, 148.60, 138.39, 137.73,
131.76, 130.47, 128.52, 126.95, 124.58, 122.78, 122.09, 121.04,
118.76, 114.52, 111.90 (aromatic and --CH.dbd.CH.sub.2), 69.05,
68.78 (Ar--O--CH.sub.2--), 64.43, 64.39 (--COO--CH.sub.2--), 28.98,
28.87, 28.53, 25.64 (alkoxy-CH.sub.2), 19.99 (Ar--CH.sub.3).
[0281] Thermal behavior: Cr 132 N 143 I (polarization
microscope)
Example 2
Preparation of a Cholesteric Liquid Crystal Mixture
[0282] A solution consisting of 20 parts of a cholesteric mixture
consisting of 93.85% by weight of the achiral tetraacrylate 14c and
6.15% by weight of the chiral compound of the formula B 41
[0283] is dissolved in 77 parts of methyl ethyl ketone together
with 3 parts of Irgacure 184 (1-hydroxycyclohexyl phenyl ketone)
photoinitiator. The resulting mixture is applied to a 15 .mu.m
polyethylene terephthalate film using a casting apparatus, dried at
60.degree. C. and crosslinked by irradiation with UV light, as
described in WO-A-99/11733. The dry layer thickness was 2.5 .mu.m.
The layer exhibited a viewing angle-dependent color with
.lambda..sub.max=611 nm.
* * * * *